He isn't travelling to work (7)
I believe the answer is:
tourist
'he isn't' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'travelling to work' is the wordplay.
'travelling' becomes 'tour' (tour is a kind of travelling).
'to work' becomes 'ist' (I can't justify this - if you can you should believe this answer much more).
'tour'+'ist'='TOURIST'
Can you help me to learn more?
(Other definitions for tourist that I've seen before include "One travels for pleasure" , "Person travelling for pleasure" , "someone on holiday" , "Cheap travel class" , "Traveller for pleasure" .)